Since about two weeks the perfomance of Thunderbird is much slowed by regular appearing of the words "Does not react". This can occur at any time - when writing, when opening an attachment... If I wait long enough (sometimes minutes) it functions normal again, but can fall back in the same error at any time. Is this due to the continuous updates of Microsoft? An overworking of an anti-virusprogram? When I check "help" I use the latest and updated version of Thunderbird. Any suggestions?